How is ankylosing spondylitis inherited?
Although ankylosing spondylitis (AS) can occur in more than one person in a family, it is not a purely genetic disease. The cause of AS is unknown. Most likely it is a combination of genes and the environment that play a role in determining the risk of developing AS. The main gene associated with a risk for getting AS is called HLA-B27.
However, inheriting the genetic variation linked with AS does not mean a person will absolutely develop the condition, even in families in which more than one family member has the disorder. For example, ~80% of children who inherit HLA-B27 from a parent affected with AS do not go on to develop the disorder.